Borehole fluid telemetry systems, often referred to as mud pulse systems, use borehole fluid, such as so-called drilling mud, as a medium to transmit information from the bottom of a borehole to the surface. Such information is useful during operations for the exploration and/or discovery of hydrocarbons such as oil and gas. Virtually any type of data that may be collected downhole can be communicated to the surface using borehole fluid telemetry systems, including information about the drilling operation or conditions, as well as logging data relating to the formations surrounding the well. Information about the drilling operation thus transmitted may include, for example, pressure, temperature, direction and/or deviation of the wellbore, as well as drill bit condition. Formation data may include, by way of an incomplete list of examples, sonic density, porosity, induction, and pressure gradients of the formation. The transmission of this information is important for control and monitoring of drilling operations, as well as for diagnostic purposes.
Borehole fluid telemetry systems produce fluid pulse telemetry signals comprising transient borehole fluid pressures variations. The fluid pulse telemetry signals often comprise data pulses produced by a valve arrangement (e.g. a rotary shear valve or a poppet valve). The rate of data pulse production, and therefore of transmission bandwidth, may be limited by the mechanics of the particular apparatus used in generating fluid pulses downhole.